public class Text1 {
    public static void main(String[] args) {
        int  flag = -1;
        double sum = 0;
        for (int i = 1; i <=100 ; i++) {
            if(i % 2 == 0 ){
                sum += flag*(1.0 / i);
            }else{
                sum += (1.0 / i);
            }
        }
        System.out.println(sum);
    }
}
